The present invention relates to the reduction of an electromagnetic noise generated by the magnetic vibration of the claw-shaped magnetic pole portion of a vehicle alternator having a Lundell-type rotor.
FIG. 17 is a view showing the arrangement of a conventional vehicle alternator, and FIG. 18 is an enlarged sectional view showing the vicinity of the poles and bobbin of a rotor.
In the respective drawings, a rotor 1 is composed of a pair of claw-shaped poles 2 each having a plurality of claws 2a formed thereto, a bobbin 3 around which a coil 4 is wound, a rotary shaft 5 and a slip ring 6. The pair of poles 2 are disposed in confrontation with each other so that the claws 2a are meshed with each other and the rotary shaft 5 is fixed by being press fitted into the axial center position of the claws 2a. The inner peripheries 2b of the base portions of the claws 2a are abutted against the outer periphery 3a of the bobbin 3 which is fixed between the pair of poles 2 by the press fitting force of the rotary shaft 5. A stator 7 is disposed to the outer peripheries of the poles 2 with a slight interval defined therebetween. A voltage controller is mounted to a brush holder 8. A pulley 10 is mounted to the rotary shaft 5 integrally therewith and fans 11 are mounted to the end surfaces of the poles 2 integrally therewith. A front bracket 12 and a rear bracket 13 are disposed to surround the rotor 1 while journaling the rotary shaft 5.
Next, operation of the conventional alternator will be described.
A current is supplied to the coil 4 through the brush holder 8 and the slip ring 6 and at the same time the pulley 10 is driven in rotation by a belt to thereby permit the stator 7 to generate an alternating current. The alternating current is converted into a direct current by a rectifier 9. While the alternator is in operation, a magnetic attracting force is imposed on the poles 2 by the magnetic flux in the interval between the poles 2 and the stator 7. The magnetic flux continuously changes as a time elapses and the magnetic attracting force acts on the poles 2 as a swaying force so that the poles 2 are swayed as shown by the arrow in FIG. 18. The resonant vibration of the poles 2 generates a so-called electromagnetic noise. Since the conventional vehicle alternator is arranged as described above, there is a problem that the magnetic attracting force acts to sway the poles 2 to thereby generate the electromagnetic noise.
As means for reducing the electromagnetic noise, there is conventionally employed such a countermeasure that a ring 14 is abutted against the insides of the claws 2a to increase the rigidity of the poles 2 and the resonant vibration of the poles 2 is shifted to a high frequency region as shown in FIG. 19. However, only the shift of the resonant vibration to the high frequency region is not any solution to the root of the matter for reducing the level of the electromagnetic noise and further since the number of parts is increased, a cost is made expensive.
An object of the present invention made to solve the above problems is to provide a vehicle alternator capable of effectively reducing an electromagnetic noise.
A vehicle alternator according to the present invention including steel sheet fans mounted to poles by being welding to the end surfaces of the poles on the inner peripheral sides of the fans at a plurality of positions in a peripheral direction and a bobbin around which a coil is wound and which is attached in the poles is arranged such that it includes elastic matters interposed between the fans and the poles on the outer peripheral side of the welding portions where the fans are welded to the poles.
A vehicle alternator according to the present invention including steel sheet fans mounted to poles by being welding to the end surfaces of the poles on the inner peripheral sides of the fans at a plurality of positions in a peripheral direction and a bobbin around which a coil is wound and which is attached in the poles is arranged such that it includes vibration-proof rings mounted to the outer peripheral edges of the poles on the fan side thereof and elastic matters interposed between the poles and the vibration-proof rings.
A method of manufacturing a vehicle alternator according to the present invention includes the steps of applying the paste of an elastic material to fans on the outer peripheral side of the welding positions where the fans are welded to poles, integrating the fans with the poles by welding the fans to the poles while pressing the coated surfaces of the elastic material against the end surfaces of the poles and curing the elastic material.